Of all the words a proud, ambitious man might use to describe himself, perhaps only Abraham Lincoln would choose strange. Yet there it is. In one of his earliest wisps of autobiography, Lincoln wrote that he was “a strange, friendless, uneducated, penniless boy” when he emerged from the backwoods in his early 20s to make his way in the world. Editors of Lincoln’s Collected Works found the word so perplexing that they added an r to transform him into a mere stranger. But the late David Herbert Donald, one of Lincoln’s most admired biographers, astutely recognized that the man meant what he said.

Strange can mean odd or quirky, and Lincoln was certainly that. His foes nicknamed him the Gorilla, which captures his long-armed, shambling animal strength. His hands and feet were enormous, and his brow was simian. Yet when he spoke, a high and reedy voice twanged forth incongruously. At one moment, he might be braying loudly over one of his own salty jokes, and at the next, lost in catatonic silence.

Strange can also mean unfamiliar, alien. This too is Lincoln, who never quite fit in. The youthful Lincoln was a rawboned genius on an uncomprehending frontier. As President, he was a self-taught rustic surrounded by the polished burghers of Eastern society. Magnetic, keenly sensitive, often able to understand others better than they understood themselves, Lincoln was nevertheless profoundly isolated. Perhaps the early deaths of his mother and sister steeped him in sorrow so thoroughly that he learned to prefer loneliness to intimacy. He “never had a confidant,” his law partner William Herndon wrote. “He was the most reticent and mostly secretive man that ever existed.”

Despite interviewing dozens of Lincoln’s associates in the months after his death, J.G. Holland, an early biographer, found himself stumped. “There are not two who agree in their estimate of him,” he wrote. One would say “he was a very ambitious man”; another would assert “that he was without a particle of ambition.” People said that “he was one of the saddest men that ever lived, and that he was one of the jolliest men that ever lived … that he was a man of indomitable will, and that he was a man almost without a will; that he was a tyrant, and that he was the softest-hearted, most brotherly man that ever lived.” The real Lincoln, Holland concluded, was the sum of his contradictions.